Ship boarding in a pirate game?

Hi Im making a adventure/strategy game similar to sid meiers pirates. It's set in the 17th century Caribbean. Typically when you board an enemy ship in such games you can keep it. However this makes aquiring new ships rather trivial, as boarding ships is the main gameplay mechanism and as such, you frequently board ships. Would it seem very strange if you are never given the option to keep the boarded ship (add it to your convoy)? You instead board ships simply to steal plunder and new ships can only be aquired by buying them from shipwrights in ports.